In order to investigate mixing uniformity in microwave reactor, the microwave reactors with dual stirring structure were designed, combined by the upper and lower impellers A100(A1), the upper impeller A200 and lower impeller A100(A2), and the upper impeller A100 and lower impeller A200(A3). Based on Computational Fluid Dynamics (CFD) method, laminar model, component diffusion model and multi-reference frame method (MRF) were used to simulate flow mixing characteristics of the alcohol-oil mixture in these microwave reactors. The flow characteristics of the alcohol-oil mixture and mixing time characteristics at different feeding positions in these microwave reactors were obtained. The results showed that there was a circulation flow surface with axial velocity approaching zero between the upper and lower impellers in microwave reactor with combined impeller A1, which affected the axial flow mixing of the mixture. The combined impeller A2 and A3 improved the axial velocity distribution on circulation flow surface, with the maximum axial velocity 1.22 times and 2.28 times of the combined impeller A1, respectively. Meanwhile it enhanced the axial migration capability of mixture between the upper and lower impeller. The position of the feeding point could affect the mixing time of mixture in microwave reactor. The combined impeller A3 obtains the shortest mixing time at the ideal feeding point B. The study provided a practical theoretical reference for the design, selection and application of the microwave reactor combined impellers.